In accordance with a rapid spread of information relevant apparatuses and communication apparatuses such as a personal computer, a video camera and a portable telephone in recent years, the development of a battery to be utilized as a power source thereof has been emphasized. The development of a high-output and high-capacity battery for an electric automobile or a hybrid automobile has been advanced also in the automobile industry. A lithium battery has presently drawn attention, from the viewpoint of a high energy density among various kinds of batteries.
There have been conventionally attempts to improve performance of a lithium battery in the field of such lithium batteries, while focusing on an interface of an electrode active material. For example, in Non Patent Literature 1 and Patent Literatures 1 to 3, a technique for forming a coating layer on the surface of a cathode active material of a lithium battery is disclosed.
Specifically, in Non Patent Literature 1, a technique for coating the surface of a cathode active material comprising LiNi0.5Mn1.5O4 with Li3PO4 by using an electrostatic atomizing method is disclosed. Also, in Non Patent Literature 1, it is disclosed that Li3PO4 coated by an electrostatic atomizing method is crystallized by heat-treating at 400° C. for 20 minutes.
Also, in Patent Literature 1, a technique for forming a coating layer in such a manner that Al2O3 and Li3PO4 are coated on the surface of a cathode active material of a lithium manganese complex oxide and heat-treated by a liquid phase method is disclosed. In addition, in Patent Literature 2, a technique for forming a coating layer in such a manner that ZrO2, Al2O3 or TiO2 are coated on the surface of a cathode active material composed of LiNiCoMnO2 and heat-treated at 400° C. or less by a pulsed laser deposition method is disclosed. Furthermore, in Patent Literature 3, a technique for coating the surface of a cathode active material composed of LiCoO2 with Li3PO4 and Li4SiO4 by using a PLD method is disclosed.